In recent years toners have been desired to have smaller particle sizes from the viewpoint of achieving even higher image qualities. Processes for preparing toners include a melt-kneading and pulverization method, and a wet process such as an emulsification and aggregation method. When a toner containing a resin binder containing a crystalline polyester as a main component is prepared by the melt-kneading and pulverization method, it is difficult to control the pulverization, thereby making it impractical.
JP2004-198598 A and JP-A-Hei-9-311502 each discloses an invention relating to the preparation of a toner by an emulsification and aggregation method, which is a wet process. However, in the process described in JP2004-198598 A, an applicable resin binder is limited to one that is soluble in an organic solvent, and in the case of a resin having low solubility in an organic solvent, the yield of toner is dramatically lowered. In addition, in the process described in JP-A-Hei-9-311502, although an aqueous medium is used in place of an organic solvent, fine particles are formed by a mechanical means, a specialized disperser is necessitated to obtain a mechanical force for forming particles having smaller sizes.
In addition, JP2002-296839 A and JP-A-Hei-7-333890 each discloses an invention using a masterbatch of a colorant in a wet process. However, in the process described in JP2002-296839 A, an applicable resin binder is limited to one that is soluble in an organic solvent, and in the case of a resin binder having low solubility in an organic solvent, the yield of toner is undesirably dramatically lowered. In addition, even in the solvent suspension method described in JP-A-Hei-7-333890, not only a resin binder is limited to one that is soluble in an organic solvent, but also a particle size of a droplet which can be prepared by a suspension method is limited, so that the toner is limited in controlling its particle size and particle size distribution.